The present application is based on and claims under 35 U. S. C. xc2xa7 119 with respect to Japanese Patent Application No. 2002-281495 filed on Sep. 26, 2002, the entire contents of which are incorporated herein by reference.
The present invention is generally directed to valve timing control device. More particularly, the present invention pertains to a valve timing control device for controlling an opening and closing time of at least one of an intake valve and an exhaust valve of a internal combustion engine on the basis of the running condition of a vehicle-mounted internal combustion engine.
In general, the variable valve timing control device comprising: a drive member rotatable in synchronization with a crankshaft, a rotatable driven member connected to a camshaft arranged co-axially with the drive member, a hydraulic chamber formed at one of the drive member and the driven member, a vane dividing the hydraulic chamber into an advanced angle chamber and a retarded angle chamber, a relative rotation phase controlling mechanism which controls a relative rotation phase between the drive member and the driven member between a most retarded angle phase in which a volume of the advanced angle chamber is a maximum and a most advanced angle phase in which a volume of the retarded angle chamber is a maximum by supplying or discharging operation fluid to and/or from the advanced angle chamber and the retarded angle chamber.
Further, the variable valve timing control device comprising: a lock mechanism which restricts relative rotation between the drive member and the driven member, when the relative rotation phase is a predetermined lock phase between the most advanced angle phase and the most retarded angle phase at the engine start in order to prevent the vane from oscillating in the fluid pressure chamber by periodical fluctuation torque of a cam causing by the camshaft opening and closing the valve and obtain the smooth startability of the engine and the adjusting width extending to both advanced angle direction and the retarded angle direction of the relative rotation phase of the both rotation member
Aforesaid lock mechanism biases a lock body provided on the rotatable drive member to the rotatable driven member side by a spring and insert the aforesaid lock body into the lock oil chamber provided on the rotatable driven member and restrain the aforesaid relative rotation and obtain lock status. On the other hand aforesaid lock mechanism draw back the lock body to the rotatable drive member side by supplying lock oil in the lock oil chamber and providing oil pressure and unlock the aforesaid lock status
A known valve timing control device of the general kind is disclosed in Japanese-Laid-Open 2001-50063, and it detects the relative rotation phase between the rotatable drive member and the rotatable driven member at the engine stop upon input of a signal indicating engine stop from the ignition key switch and feedback-controls the aforesaid relative rotation phase control mechanism and adjust the relative rotation phase of both rotation members to lock phase side and restrains the aforesaid relative rotation and obtain lock status by the aforesaid lock mechanism.
By the way, although the aforesaid control mechanism of the aforesaid valve timing control device needs to drain lock oil from the lock oil chamber and obtain the aforesaid lock status during the relatively short time from input of a signal indicating engine stop from the ignition key switch to rotation stop of the crankshaft. The aforesaid control mechanism of the aforesaid valve timing control device occasionally can not obtain the aforesaid lock status when the engine oil is yet low temperature and of high viscosity while the engine is not warm.
Therefore, A known valve timing control device of the general kind is disclosed in Japanese-Laid-Open 2001-355468, and it passes the relative rotation phase of both rotation member through the lock phase and obtains the lock status by the lock mechanism by making the advanced angle chamber, the retarded angle chamber and the lock oil chamber at drain status when the crankshaft is compulsorily rotated by the starter upon input of a signal indicating engine stop from the ignition key switch (hereinafter called cranking) and oscillating the aforesaid vane in the fluid pressure chamber by the fluctuation torque of the cam in order to obtain the aforesaid lock status at the engine start.
The causes of preventing the aforesaid lock status from being obtained are that the remaining operational oil in the advanced angle chamber or the retarded angle chamber prevents the relatively rotation, in other word, the oscillation in the fluid pressure chamber between the rotatable drive member and the rotatable driven member and that the remaining oil in the lock oil chamber prevents the lock body from inserting into the lock oil chamber.
Especially in case that the engine oil is low temperature as the engine not warm and the engine is restarted immediately after the engine stops, the operational oil in the advanced angle chamber or the retarded angle chamber and the lock oil in the lock oil camber occasionally can not be drained perfectly because the engine oil is yet low temperature and of high viscosity. In case that the lock oil is not drained perfectly from lock oil chamber the aforesaid lock oil prevent the relative rotation of both rotation member and the insert of the lock body and the lock status can not be obtained.
It is, therefore, an object of the present invention to provide an improved valve timing control device which overcomes the above drawbacks.
It is another object of the present invention to provide an improved valve timing control device which obtains exactly the lock status to restrain the relative rotation between the rotatable drive member and the rotatable driven member.
The invention provides a variable valve timing control device comprising: a drive member rotatable in synchronization with a crankshaft, a rotatable driven member connected to a camshaft arranged co-axially with the drive member, a hydraulic chamber formed at one of the drive member and the driven member, a vane dividing the hydraulic chamber into an advanced angle chamber and a retarded angle chamber, a relative rotation phase controlling mechanism which controls a relative rotation phase between the drive member and the driven member between a most retarded angle phase in which a volume of the advanced angle chamber is a maximum and a most advanced angle phase in which a volume of the retarded angle chamber is a maximum by supplying or discharging operation fluid to and/or from the advanced angle chamber and the retarded angle chamber, a lock mechanism which restricts relative rotation between the drive member and the driven member, when the relative rotation phase is a predetermined lock phase between the most advanced angle phase and the most retarded angle phase, a control mechanism performing an intermediate phase operation upon input of a signal indicating engine stop to position the relative rotation phase intermediate between the most advanced angle phase and the most retarded angle phase by operating the relative rotation phase controlling mechanism, and performing a drain operation to drain the operation fluid from both the advanced angle chamber and the retarded angle chamber after performing the intermediate phase operation.